Mechanical behavior of interlayer soil in ancient railway sub-structure

The study, described in this paper, deals with the effects of fines and water content on the mechanical behaviour of interlayer soil, by carrying out large-scale monotonic and cyclic triaxial tests. The results of monotonic triaxial tests show that adding more fines in the interlayer soil does not significantly change the shear strength under dry condition but drastically decreases the shear strength parameters (friction angle and cohesion) in the nearly saturated condition. The cyclic triaxial tests were carried out at various deviator stress levels. By considering the permanent axial strain at the end of application of each stress level, it is observed that in the nearly saturated condition, the higher the fines content the larger the permanent axial strain. In the case of lower water contents, an opposite trend is identified: adding fines decreases the permanent axial strain.